The present invention is an improved vise for gripping elongated objects such as pipe used in the oil and gas producing industry. The vise is designed to restrain the rotation of such objects while the objects are in the vise's grip.
The vise finds particularly useful application in the hydraulic testing of casing and other large diameter pipe used in the production of oil and gas. The hydraulic testing of such pipe is generally accomplished by mounting and securing the pipe on a hydraulic pipe testing apparatus, sealing both ends of the pipe with watertight plugs, introducing hydraulic test fluid into the pipe through an aperture in one of the plugs, filling the pipe with the hydraulic test fluid, increasing the hydraulic pressure on the hydraulic test fluid in the pipe to a pre-determined level and then visually inspecting the external areas of the pipe to check for leaking hydraulic test fluid. When pipe is tested with hydraulic test fluid under high test pressure, structurally flawed pipe may burst due to the great internal pressure of the hydraulic test fluid on the walls of the pipe.
Both rotational and translational forces may act upon a pipe when it is mounted in a pipe testing apparatus. Translational forces tend to cause the pipe to move laterally or vertically with respect to the apparatus and rotational forces tend to cause the pipe to rotate either clockwise or counterclockwise with respect to the apparatus. Because the rotary motion of the pipe can cause the vise jaws securing the pipe to the pipe testing apparatus to loosen and permit the pipe to be thrown from the apparatus, it is very desirable for a vise to have the capability to restrain the rotational motion of a pipe clamped in the vise's grip. Because the possibility exists that the pipe may reverse its direction of rotation quickly and unexpectedly, it is also desirable that the vise have the capability to automatically adjust its mode of operation to restrain either clockwise or counterclockwise rotary motion. In addition to the foregoing, the vise must have sufficient strength to restrain the pipe against any translational forces acting upon it.
The improved vise which comprises the present invention meets the requirements set forth above. As will be more fully discussed below, the improved vise of the present invention utilizes the rotational forces acting upon the pipe to tighten the vise's grip on the pipe. The vise is constructed so that any force tending to rotate the pipe is transmitted to the vise and is translated into a gripping force to be utilized by the vise jaws of the vise.